Pneumatic hammer.



C. H. SHAW.

PNEUMATIC HAMMER. APPLICATION FILED mm: 1. 1914.'

Patented June 13, 1916.

3 SHEETS-SHEET S- I'Difnesses attorneys H E COLUMBIA PLANOORAPH c0., WASHINGTON, h. c.

v C. H. SHAW.

PNEUMATIC HAMMER.

APPLICATION HLED JUNE 1, 1914. 1,187,395, Patented June 13, 1916.

3 SHEETS-SHEET 2.

inventor attorneys witnesses c. H. SHAW.

PNEUMATIC HAMMER.

APPLICATION FILED JUNE 1. 1914.

Patented June 13, 1916.

3 SHEETS-SHEET 3.

Em i

r o t n e n n 3 witnesses 3g attorneys PNEUMATIC HAMMER.

Specification of Letters Patent.

Patented June 13, 1916.

Application filed June 1, 1914. Serial No. 842,175.

of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to pneumatic hammers and has for an object to provide a hammer of improved type wherein the piston itself acts as the valves for controlling the flow of the actuating fluid.

A further object of the invention is to provide in a pneumatic hammer having a cylinder and a dilierential piston with rear end smaller than the front end and a rearwardly facing shoulder formed by the reduction intermediate the ends, means for conducting air under tension to a point in termediate the ends of the cylinder from which point it is supplied constantly to said shoulder and intermittently to the cylinder at the opposite ends of the piston, the flow of the actuating fluid to the opposite ends of the piston being controlled by the 'recipro cation of the piston itself.

With these and other objects in view the invention comprises certain novel constructions, combinations and arrangement of parts as will be hereinafter more fully clescribed and claimed.

In the drawings: Figure I is a longitudinal diametrical sectional view of the hammer with the piston shown in side elevation and at its forward or striking limit. Fig. II is a longitudinal diametrical sectional view of the cylinder with the piston at its rearwapd limit, the piston and cylinder head being shown in section. Fig. III is a transverse sectional view taken on line -33 of Figs.

I and II. Fig. IV is a transverse sectional view taken on line 1 1 of Figs. I and II. Fig. V is a view of the hammer in end elevation as indicated by arrow 5 at FigsI and II. Fig. VI is a sectional view through the cylinder with the piston removed, the plane being on radii but not a diameter. Fig. VII

, is an end View f-the cylinder with the heads removed as indicated by line 7-7 of Fig. VI. Fig. VIII is a transverse sectional view of the cylinder with the piston removed as taken on line 8-8 of Fig. VI. Fig. IX is a transverse sectional view of the cylinder with the piston removed as indicated by line 99 of Fig. VI. All of Figs. VII, VIII and IX show position lines 66 upon which radii Fig. VI is projected.

The improved pneumatic hammer which forms the subject matter of this application comprises a cylinder 10 preferably though not necessarily flattened upon opposite sides as indicated at Figs. III, IV, V, VII, VIII and IX. At its forward end the cylinder is provided with a tappet 11 engaging against a drill 12, all in substantially the usual and ordinary manner and forming no particular part of the present invention.

At its rearward end fluid under tension is admitted at 13 to a chamber 14 from which passages 15 lead to an annular chamber 16 intermediate the ends of such cylinder from which chamber 16 the fluid under pressure is carried and admitted to the various desired points in the cylinder and piston by passages and other means as hereinafter described and at which annular chamber the.

constant pressure of the fluid is applied to the piston.

Passages 17 are provided separated from chamber 16. by ribs 18, the interior curvature of which correspond to the general diameter of the cylinder at that. point. Within the cylinder a piston 19 is mounted to reciprocate having a portion 20 corresponding to the general diameter of the cylinder at the ribs 18 so that as the said portion 20 is located at the ribs 18 communication between the annular chamber 16 and the passages 17 is interrupted. The piston is also provided with an annular groove 21 which permits communication between such chamber 16 and the passages 17 as indicated more particularly at Fig. II. The piston is also pro vided with an enlarged head producing a shoulder 22 against which at all times pressure from the chamber 16 operates. With the parts located as shown at Fig. II, therefore, the fluid under tension from the chamber 16 passes over the ribs 18 and through the passages 17 to the rear of the piston acting upon the rear of the piston and also upon the shoulder 22 to force the piston for ward in the cylinder into engagement with the tappet 11 as shown at Fig. I. Passages 2d are provided separated from annular chamber 16 by ribs 23 the interior curvature of which correspond to the general diameter of the cylinder at that point thusiorming a bore corresponding in size withthe enlarged forward portion 19 of the piston so that when the piston is in position shown in Fig. II, communication betweenannular chamber 16 and passages 2 l wlll be inter? rupted but will be reestablished as soon as;

shoulder 22 passes beyond ribs 23-on forward stroke as shown at Flg. I. The movement of the piston in this direction also serves to bring the part 20 ofthe piston into engagement with the rib 18 to close communication between the chamber 16 and the passages 17 and thus cutoff the supply to the rear of the piston of fluid under pressure and simultaneously to uncover ports which communicate with exhaust passages 26 so that the fluid under tension at the rear of the piston is exhausted through the ports .25 and passages 26. The fluid under tension, however, at this point is, of course, applied to the forward end of the piston and V the tension being relieved from the rear or portion 20 of the piston and the area of the front end of the piston being much larger than the area of shoulder 22, against which the pressure is constant, the piston is forced rearwardly to again cover the ports 25 and form an air cushion in the rear or portion 20 of the piston and to simultaneously cut off the fluid under. pressure from theiforward end of the piston by bringing the enlarged end of the piston into engagement with the ribs 23 and apply the fluidunder tension to the rear of portion 20 of the piston by removingthe part 20 of thepiston from the ribs 18'. Also simultaneously the bleeders 27 are uncovered which communicate with the ports 28 also next uncovered, the ports 28' communicating with the passages 29 which form reduced continuations of the exhaust passages 26-. The uncovering of th'ebleeders 27 which are small reduce the pressure only slightly, the entire exhaust awaiting the uncovering of the ports 28 which. serve to exhaust the pressure at the forward end of the piston permitting the air cushion in and at the rear of the piston to check the momentum of the return stroke, and'the application of the live fluid also in. and at the rear of the piston to- .gether with the constant pressure on the shoulder 22 to start the piston on its striking stroke to repeat the operation as before described. On the forward stroke of the piston the ports 28 serve to permit the escape of the air compressed at the front of the piston till the piston has covered such ports 28 whereupon additional exhaust is provided by the bleeders 27 at a point nearer the forward end of the stroke than the port 28. His obvious of course, that by the time the port 28 hasbeen covered the piston is near .ing the forward end of its-str0ke,but it is desirable that onthe forward stroke no air cushion be provided for which reason the bleeders 27 serve to relieve the compression of air at the'front of the piston, while reducing the pressure on the return stroke when the live air is admitted onlyin a very slight degree.

As will be noted at Fig. II the pistonis formed hollow and the projection 30 of the rear cylinderhead isextended into the hollow of the piston. Thisserves the'purpose of reducing the cubical area'of the chamber and at the same time permitting of the pisit'on being formed long enough to .prevent its binding in the cylinderand yet not to increase its weight beyond the desired weight for producing the stroke desired.

It will be noted that the fluid under tension being at all times in the annular chamber. 16 requires lntermlttent movement of such fluid. only one-half the length of the cylinder for either stroke of the piston in stead. of a short passage for one stroke and a long passage for another stroke as is customary in such hammers. by reducing the length of the passage" from the point of constant supply of fluid pressure to its point of operation quicker action is possible and greater rapidity of piston action is the result. While the constant 'application of the fluid pressure to the shoul der of the piston serves tostart the piston on its forward or striking stroke without waiting for theapplication of the intermittently applied air in and at the rear of the piston and also serves to prevent excessive move ment or momentum of the hammer on its return stroke when no work is to be 30001111 plishcd by such, stroke.

. I claim:

1. In a pneumatic hammer, a cylinder, a

piston therein, saidpiston having its rear 7 portion reduced'in diameter, means to con-V.

stantly supply. fluid under pressure to the piston at the point of reduction and means to supply fluid under pressureintermittently to the ends of said piston.

2. In a pneumatic hammer, a cylinder, a piston therein, said piston having its rear portion-reduced in diameter, means to con- In other words stantly supply fluid under pressure to the piston at the point of reduction and means to supply fluid under pressure alternately to the front and rear ends of saidv piston.

3. In a pneumatic hammer, a cylinder, a

piston therein having itsv rear portion reduced in diameter and bored, means to constantly supply fluid under pressure to the piston at thepoint of'reduction and means to supply fluid under pressure alternately to the front end and to the bore in thesaid rear portion.

4-. In apneumatic hammer,- acylinder, a i plston therem'ha-vlng a rear end of smaller diameter than its front end and having a bore therein and a rearwardly facing shoulder intermediate said ends, means to consta-ntly apply fluid under pressure to said shoulder and means to supply fluid under pressure alternately to the rear and front ends of said piston.

5. In a pneumatic hammer, a cylinder, a piston therein having a rear end ofsmaller diameter than its front end and having a bore therein and a rearwardly facing shoulder intermediate said ends, means to constantly apply fluid under pressure to said shoulder and means to supply fluid under pressure alternately to the bore at the rear and to the front end of the piston.

6. In a pneumatic hammer, a cylinder having an annular chamber intermediate its ends and means to supply fluid under pressure to such chamber; passages leading to the opposite ends of the cylinder; a piston having a rearwardly facing shoulder intermediate its ends subjected at all times to the pressure and having other portions to serve as valves to intermittently permit the fluid pressure to pass from the intermediate chamber through said passages alternately to the opposite ends of the piston.

7. In a fluid operated percussive tool, a cylinder having a forward bore and a rearward bore, a piston having a head in said forward bore and a shank in said rearward bore, a fluid passage for conveying fluid constantly tothe rear face of said piston head,

Goplen of this patent may be obtained for passages for conveying fluid alternatelyto the forward end of said forward bore and to the rear end of said rearward bore, and

exhaust passages for the alternately supplied cylinder portions.

8. In a fluid operated percussive tool, a cylinder having a forward bore and a com municating rearward bore of smaller diameter, a piston having a head fitting in said forward bore, a shank fitting said rearward bore and a depression between said head and shank, a fluid inlet passage for constantly admitting fluid pressure to the rear end of the forward bore, a passage for conveying fluid from the rear end of the forward bore to the forward end of the forward bore at the forward end of the piston stroke, a passage from the forward end of the rear cylinder bore to the rear end of said rear cylinder bore, so placed as to be connected with said rear end of the forward cylinder bore by said depression at the rear end of the piston stroke, and exhaust ports for the front and rear ends of said cylinder.

In testimony whereof I afiix my signature 1n. presence of two witnesses.

CHARLES H. SHAW.

\Vitnesses:

CABLE IVHITEHEAD, ALBERT L. VOGL.

five cents each. by addressing the "Commissioner of Patents, Washington, D. 0. 

